The disclosure relates to a beam regulating apparatus for an EUV illumination beam. Furthermore, the disclosure relates to a position sensor device for use in such a beam regulating apparatus, an optical system including such a beam regulating apparatus, and a metrology system including such an optical system.
US 2008/0 017 810 A1 discloses an EUV light source in which a beam impingement position of a laser constituting part of the light source is readjusted.
U.S. 2009/0161093 A1 discloses systems and methods for lithographic illuminator beam deviation measurement and calibration using grating sensors. U.S. Pat. No. 4,140,398 discloses a laser autoalignment system using distortion compensated reflection grating.